Lab: Components

Introduction

In this lab you will find some of the components you’ll use frequently when making electronic circuits. For more on any given component, please check out its datasheet. There are no specific activities in this lab other than to examine the components and to familiarize yourself with them.

A datasheet or spec sheet is a document (printed or .pdf) that describes the technical characteristics of a sensor, electronic component, product, material or other. It includes details on how to use the component in a circuit and other useful design info on how to integrate it into a system together with specifications on performance and other characteristics that are important to know.

Components

Voltage Regulator

Voltage regulators take a range of DC voltage and convert it to a constant voltage. For example, this regulator, a 7805 regulator, takes a range of 8 – 15 volts DC input and converts it to a constant 5-volt output.

Note the label on the regulator that reads “7805”. Check the label on every component. This physical form factor, called the package, is used by many different components, and not all of them are voltage regulators. This is a TO-220 package.

The 7800 series regulators come in many different voltages. 7805 is a 5-volt regulator. 7809 is a 9-volt regulator. 7812 is a 12-volt regulator. All the regulators of this family have the same pin connections. In the image above, the left leg is connected to the input voltage. The middle leg is connected to ground. The right leg is the output voltage.

LED

LEDs, or Light Emitting Diodes, are diodes that emit light when given the correct voltage. Like all diodes, they are polarized, meaning that they only operate when oriented correctly in the circuit. The anode of the LED connects to voltage, and the cathode connects to ground. The anode in the LEDs in this photo is the longer leg on each LED. LEDs come in many different packages. The packages above have built-in lenses.

These LEDs are the cheapest you can buy, and they’re not very bright. You can get superbright LEDs as well, which are much brighter. If you’re working on applications that need very small light sources, you can also get LEDs in a surface mount package.

LEDs can only handle a limited amount of current and voltage. The details should be covered in each LED’s datasheet, but if not, here’s a link to a handy LED current calculator. For most common LEDs running at 5 volts, a resistor between 220 and 1K ohms will do the job.

Solderless Breadboard

Solderless breadboards are reusable prototyping tools for electronics that allow you to build and experiment with circuits simply by plugging components in and out of its rows and columns. They come in different shape and sizes.

Resistors

Resistors. Shown here are 220-ohm resistors. You can tell this because they have two red and one brown band, followed by a gold band.

Resistors resist the flow of electrical current. When placed in series, they reduce the voltage, and limit the current. The bands on a resistor indicate the resistor’s value. Here’s a handy resistor color code calculator.

Potentiometers

Potentiometers are variable resistors. The two outside terminals act as a fixed resistor. A movable contact called the wiper moves across the resistor, producing a variable resistance between the center terminal and either of the two sides.

Switches

Switches are one form of digital input. There are many kinds of switches. The two most useful categories are momentary switches, which remain closed only when you press them, and toggle switches, which stay in place after you switch them.

Pushbuttons are a common type of momentary switches. The pushbuttons in the photo above are designed to be mounted on a circuit board. They are very small, less than 1 centimeter on a side. They have four pins. When the button is facing you, top two are connected to each other, and the bottom two are connected to each other. Pushing the button connects the top pins to the bottom pins.

Toggle switches stay in one position when you flip them. Wall light switches are common examples of toggle switches. Unlike a momentary switch, a toggle switch can be used to turn a device on or off, because they stay in one state when you remove your hand. The toggle switches below each have three connectors, also called pins or legs. They’re usually labeled C for common, NO for Normally Open, and NC for Normally Closed. When you switch the switch, it will open the connection between the common pin and the normally closed pin, and close the connection between the common pin and the normally open pin. Switch it the other way, and you will reverse the connection.

Photocells

Photocells, also known as light-dependent resistors, are variable resistors whose resistance changes with the intensity of the light falling on the resistor.

Thermistors

Themistor, or temperature-sensitive resistor

Thermistors are variable resistors whose resistance changes as the temperature changes. You measure the resistance between the two legs and expose the top to a varying temperature in order to vary the resistance between the two legs.

Capacitors

Capacitors store electrical energy while there’s energy coming in, and release it when the incoming energy stops. They have a variety of uses. One common use is to smooth out the dips and spikes in an electrical supply. This use is called decoupling.

Ceramic capacitors are cheap and unpolarized. They generally have very small capacitance values. They’re useful decoupling caps in a low-current circuit. You often see them used to decouple the power going into a microcontroller or other integrated circuit.

The number on a ceramic cap gives you its value and order of magnitude. For example, 104 indicates a 0.1 microfarad (uF) cap. 103 indicates a 0.01 microfarad cap.

Electrolytic capacitor

Electrolytic capacitors can generally store more charge than ceramic caps, and are longer lasting and more expensive. They’re usually polarized, meaning that they have a positive leg and a negative leg. This is because current flows more efficiently through them one way than the other.

Electrolytic capacitor, showing the minus sign on the negative side.

An electrolytic cap will have a + or – on one side, as shown above.

Diodes

Diodes. Shown here are 1N400x power diodes. The body of the component is black, and the end is silver. The silver end indicates the cathode end of the diode.

Diodes permit voltage to flow in one direction and block it in the other direction. LEDs are a type of diode, as are the 1N4001 diodes shown here. They’re useful for stopping voltage from going somewhere you don’t want it to go.

Zener Diodes

Zener diodes have a breakdown voltage past which they allow current to flow in both directions. They’re used to chop off excess voltage from a part of a circuit.

Transistors

Transistors act as electronic switches. When you put a small voltage across the base and emitter, the transistor allows a larger current and voltage to flow from the collector to the emitter. The transistor shown above, a TIP120, is a type of transistor known as a Darlington transistor. It is usually used to control high-current loads like motors.

Power Jacks

A DC Power Jack

DC Power jacks are used to connect your breadboard to a DC power supply that you can plug into a wall. They’re less common in microcontroller circuits now that USB power connectors and USB wall plugs are common, but they are still very handy when you have only a DC power supply to work with. The one above has screw terminals on the back to which you can connect wires to connect to your breadboard. This one is a 2.1mm inside diameter, 5.5mm outside diameter jack, which is a very common size.

Battery Holders

AA battery holder9V battery snap with DC power plug on it.

Battery connectors like the ones shown above are good for connecting batteries to your project. They commonly have either two round terminals for a 9-volt battery, or a DC power jack like the one shown above.

Motors

Servo Motor

A servo motor is a motor paired with an encoder (e.g. an Arduino) to provide position/speed readings and control messages in a feedback loop. This loop is used to precisely control of the servo’s degree of rotation. RC servomotors like the one shown here can only turn 180 degrees. They are often used for the rudder control on remote control planes and cars. The plastic bits shown in the photo are called horns, and they attach to the shaft to let you attach the motor to the mechanism that you want to control.

DC Motor

DC motors utilize induction (an electromagnetic field generated by current flowing through a wire coil) to rotate a central shaft. You can reverse the direction that the shaft rotates by reversing the leads powering it.

H-Bridge

H-bridge IC, L293D

An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. They are often used to control the direction of DC motors. This H-bridge is a model L293D in a DIP package (Dual Inline Package), meaning that there are pins on either side of the component.

Electromechanical Relay

Electromechanical relays: top and left views as well as inside.

Like transistors, relays are electronic switches. Electromechanical relays contain a small coil that, when energized, creates a magnetic field that moves a small metal armature to open or close an electrical contact. Relays can handle higher current than transistors and can be used for AC or DC loads. However, because they rely on a physical mechanism, they are slower and more prone to wearing out. If you want to control a relay with the Arduino, you will need to use a transistor as an intermediary because most relays draw more current than the Arduino’s output pins can supply.

Screw Terminal

two-contact screw terminal

Screw terminals are electrical connectors that hold wires in place with a clamping screw. They allow for a more secure connection than female headers and more flexibility than soldering a wire in place. There is one screw, socket, and pin per connection.

Originally written on June 24, 2014 by admin
Last modified on August 21, 2018 by Tom Igoe